Quality of service is a major concern for any wireless system. Since these systems are linked together through an electromagnetic field that propagates from the transmitter to the receiver, one must then be concerned with the transmitting and receiving antennas and the propagation path. The focus in modern wireless systems has been to develop base-station antennas that properly illuminate an assigned sector. Their patterns are rather basic in that they have a standard shape with a wide azimuth beam width and a narrow elevation beam width, which is based on line-of-sight applications. Thus, they function very well in rural applications across open fields. Unfortunately, they suffer performance degradation when used in urban applications in that the buildings block the field of view of both the transmitter and receiver. This results in complex fading illumination of the receiving antenna and reduced quality of service. To overcome this problem, wireless companies and their suppliers have focused on solving this situation by modifying the base station radiators by using dual polarized antennas, multiple space-diversity antennas, smart antennas, etc. These approaches have had some success in providing better performance, but they tend to be expensive and quite complex. As a result, the wireless industry needs a new approach that is not based on the antenna but on the propagation path.
Fundamentally, a wireless system links the transmitter and receiver through a set of complex electromagnetic propagation paths, especially in urban applications. These propagation paths follow the basic ray optical principles of reflection, transmission and diffraction, but in an urban environment, there are multiple paths that interconnect the transmitter and receiver. These multiple paths cause the signal at the receiver to fade in and out. If there is one dominant path, then the difference between the maximums and minimums is relatively small. So one approach to improve performance is to create this situation. The second approach is to deflect undesired paths away from certain areas to remove the interference and create one dominant path. A third way is to create many paths in the same region so that the illumination is so complex that the receiver senses a more stable illumination. There are other concepts, but these illustrate some general approachs that can be used to enhance wireless system performance by modifying the propagation path scenario.
One embodiment of the present invention is a reflective panel for deflecting electromagnetic waves comprised of a resistive material varying in resistivity across the panel; a center portion on the panel, having a predetermined resistivity; a periphery portion on the panel having a higher resistivity than the center portion; and wherein the center portion of the panel is adapted to reflect the electromagnetic waves and wherein the periphery portion is adapted to minimize diffractions.
In addition to the features mentioned above, objects and advantages of the present invention will be readily apparent upon a reading of the following description.